Dynamic Islands in the Wadden Sea

The ongoing geological processes in the coastal and marine environment of the Wadden Sea have been instrumental in the formation of the world’s largest temperate zone tidal flat system.

The ceaseless activity, driven by the forces of water and wind, constantly creates, re-shapes, destroys and renews geomorphic and physiographic features on a variety of spatial and temporal scales. In turn, these changes induce ecological and biological responses that create a complex coastal ecosystem teeming with plant and animal life as well as immense geological interest.
Indeed, these outstanding qualities of geology, hydrology, morphology, ecology and biodiversity have led to the entire Wadden Sea along the coasts of The Netherlands and Denmark being declared a UNESCO World Heritage Site. Criterion VIII stated that the area is an outstanding example representing major stages of Earth’s history, including the record of life, significant ongoing geological processes in the development of landforms, and significant geomorphic or physiographic features.
Large scale examples of continuous geological processes and morphological interactions are on public view in the Wadden Sea. Among the most spectacular are the creation, continual shifting and changing, and ultimate disappearance of many of the region’s uninhabited natural islands, along with all the biota they support.
In this Wadden Sea Ecosystem issue we have collected a series of papers dealing with the development of small uninhabited islands to demonstrate dynamic processes at work on different scales.
The objectives for this issue are

  • to present an overview of dynamic islands throughout the Wadden Sea,
  • to illustrate the main geomorphological features and to describe the consequences for biota,
  • to obtain an understanding of general developments and regional differences in island dynamics throughout the Wadden Sea,
  • to exemplify the value and significance of natural dynamics in the Wadden Sea to a broader public and to decision makers, and
  • to highlight the intrinsic value and importance of natural processes to the ecosystem.

These objectives are difficult to achieve. We therefore start with a couple of papers which set the scene. The articles represent the scientific views of each author. We present these articles in a geographic sequence from The Netherlands as the westernmost extremity to Denmark as the northernmost. The articles span a range of topics, from a description of dynamic islands of a complete region to geomorphological studies, botanical evaluations and inter-disciplinary analysis, and even a historical review of a vanished island.
The articles discuss islands in various states, from evolving land masses like Norderoogsand and Kachelotplate through senescent islands like Trischen and probably Mellum, to the study of human creations like Scharhörn and Nigehörn.
Most of the islands are on the move and amply demonstrate this dynamic. Moving rates proved to be very different. The highest mean shifting rates are reported from The Netherlands whereas Scharhörn, in the mouth of the inner Elbe, shows the lowest value and highest rate of stability. We see how shifting rates change over the years and are determined by sediment supply in conjunction with singular, mostly storm-related, events. Extreme weather and tide conditions, combined with changes in hydrodynamics, seem to be the drivers of dynamic changes to the islands, but of course there is the underlying influence of sea level rise.
To gain a better understanding of the value of natural dynamics on the level of whole islands we recommend a continuation of monitoring approaches on the dynamics of unprotected islands in an inter-disciplinary approach. The TMAP standards are a good starting point.
 

Hellwig, U. and Stock, M. (Eds.) 2014. Dynamic Islands in the Wadden Sea.
Ecosystem No. 33: 1-134. Common Wadden Sea Secretariat, Wilhelmshaven, Germany.
www.waddensea-secretariat.org, Wilhelmshaven Germany.